Ever since the advent of hard surfaced roads, the traveling public has been plagued with the problem of pot holes. The causes of these dangerous and property damaging cavities in road surfaces vary somewhat, from the southern to the northern sections of the United States. However, all stem from moisture or water seeping through cracks in pavement down into the soil beneath. This water either freezes, thus creating expansion and forces the substrata upward or washes away the substrata leaving voids beneath the paving surface. Traffic exerts pressure on this weakened area and the surface crumbles thereby creating a pot hole.
The pot hole problem is worsening every year. Between 1960 and 1980 there was an increase of 75 million registered vehicles in the United States. Thirty million of these were trucks with an ever increasing gross weight allowance. These heavy trucks have accounted for 90% of the decrease in road surface longevity.
Pot holes are filled on an average of twice a year, once with a cold patch and again with a hot patch. The hot patch is used when the mean temperature rises above freezing. During this time between fills the weight of heavy traffic dislodges the pot hole fill and causes a perpetual problem.
In northern areas, freezing and contraction of pavement surfaces causes the main problem. In southern areas, heat causes expansion and buckles the pavement surface.
Extensive use is made of asphalt paving as a means for surfacing for general traffic use, both on primary and secondary roads, as well as parking lots and, in some locations, as sidewalks. Asphalt is a dark brown to black cementitious material in which the predominating constituents are bitumens which occur in nature or are obtained in petroleum processing. The Asphalt Institute considers the term "asphalt" to include asphalt cements, asphalt fluxes, asphalt cutbacks, asphalt emulsions, asphalt road oils, roofing and waterproofing asphalts and all other asphalts and asphalt residuums used in the manufacture of asphalts and asphalt specialties. Such widespread use creates and ongoing demand for repair and preventative maintenance. Over prolonged periods of time, for various reasons, the asphalt surface deteriorates or fails or is otherwise damaged and requires repair. Pavements in need of maintenance or repair can exhibit any or all of the following conditions:
"Raveling" is the progressive separation of aggregate particles in a pavement from the surface downward. Usually, the fine aggregate comes off first and leaves little "pock marks" in the pavement surface. As the process continues, larger and larger particles are broken free, and the pavement soon has the rough and jagged appearance typical of surface erosion. Raveling can result from lack of compaction during construction, construction during wet or cold weather, dirty or disintegrating aggregate, poor mix design, or extrinsic damage to the pavement.
"Shrinkage Cracks" are interconnected cracks forming a series of large blocks, usually with sharp corners or angles. They are caused by volume changes in the asphalt mix, in the base, or in the subgrade. "Alligator Cracks" are interconnected cracks forming a series of small blocks resembling an alligator's skin or chicken wire. In most cases, alligator cracking is caused by excessive deflection of the surface over unstable subgrade or lower courses of the pavement. The unstable support usually is the result of saturated granular bases or subgrade. The affected areas in most cases are not large; sometimes, however, they will cover entire sections of a pavement, and when this happens, it usually is due to repeated loadings exceeding the load-carrying capacity of the pavement.
"Upheaval" is the localized upward displacement of a pavement due to swelling of the subgrade or some portion of the pavement structure. In colder climates, upheaval is commonly caused by expansion of ice in the lower courses of the pavement or the subgrade. It may also be caused by the swelling effect of moisture on expansive soils.
"Pot Holes" are bowl-shaped holes of various sizes in the pavement, resulting from localized disintegration of the pavement under traffic. Contributory factors can be improper asphalt mix design, insufficient pavement thickness, or poor drainage. Also, pot holes may simply be the result of neglecting other types of pavement distress.
"Grade Depressions" are localized low areas of limited size which may or may not be accompanied by cracking. They may be caused by traffic heavier than that for which the pavement was designed, by settlement of the lower pavement layers, or by poor construction methods.
The major failure of asphalt surfacing results from moisture penetration of the base material. This penetration of moisture is generally caused and/or accelerated by overloading small units of area through numerous repetitive cycles until the asphalt covering disrupts or separates. Once this occurs, of course, moisture seeps into the base material and not only naturally deteriorates the material, but also may freeze and cause separation of large amounts or quantities of material which are reduced to small particles by continued use of the surface thus eventually causing a hole or depressed area commonly called a "pot hole" as set forth earlier.
In order to prevent or minimize this type of damage from occurring, the asphalt surface is periodically sealed with a seal coat solution that penetrates any separations or disruptions in the asphalt surface thus preventing moisture from entering therein. If, however, the pot hole occurs, one way to prevent additional damage is to trim and excavate the failed area or pot hole, remove any dust, dirt or excess material, reseal the exposed base to preclude any additional moisture from entering therein and replacing the removed asphalt surface with a cold or hot asphalt mix and tamping, compacting, or rolling the hot or cold mix until it achieves the proper density and elevation with respect to the surrounding asphalt surface.
Numerous pavements have a concrete surface rather than asphalt. One proposed method of resurfacing concrete structures has been to employ an epoxy resin such as a reaction product of epichlorohydrin and bisphenol in which polymerization is stopped before a solid product of higher molecular weight is obtained. In that application, it is essential that the epoxy resin employed be liquid in order that the composition may be applied to a damp concrete surface. The mixture further includes a polyamide resin component and a filler such as sand washed free of soluble salts and having particle size of 30 mesh or smaller. A second filler of finer particle size can also optionally be included to give better packing during application of the composition to the road surface. Coloring pigment such as iron oxide, titanium or carbon black can be included as an optional component. Illustrative of such resurfacing technique is U.S. Pat. No. 2,934,452.
Other cold patching techniques have been developed primarily for asphaltic surfaces. Once such technique involves the coating of a cold patch material or mixing such cold patch material with a solution of a thermoplastic polymeric resin. The solvent causes resin penetration into the patching material and the pavement area adjacent the patch. After the solvent volatilizes a thermoplastic resin is provided which purportedly adds strength to the patched area and provides a greater water repellency for the patched area and more firmly secures the patch to the surrounding area. In filling large pot holes, the resin solution is thoroughly mixed with the patch material and compacted in the pot hole such as by rolling or vibratory compaction. The compaction can be accompanied by heat which assists in volatilization of the solvent after the solvent has penetrated the patch and the area surrounding it. In order to obtain the best adhesion, it is preferred in this method to place some of the resin solution on the wall of the cavity prior to inserting the fill material within the cavity. The fill materials employed in this method are typically asphalt and tar. Illustrative of this method is U.S. Pat. No. 4,097,172.
Numerous patents have issued for self-contained vehicles which include hoppers for storing bituminous materials appropriate heating sources and distribution and compaction devices for filling the pot hole and compacting the fill material in the pot hole. Illustrative of such self-contained vehicles are U.S. Pat. Nos. 2,420,410 (includes means for applying heat to the outer periphery of the pot hole to assist the molten material to flow into all the cracks in a liquid condition and to maintain the material in a molten condition for the requisite time to allow full penetration); U.S. Pat. No. 4,072,435 (discloses a vehicle spreader, roller, heater combination including means for mixing asphalt with aggregate); U.S. Pat. No. 3,270,632 (discloses a vehicle including means for heating bumps in a road using a propane heat source in combination with a scraping blade to even up the bumps); U.S. Pat. No. 3,625,120 (discloses a tractor with an asphalt hopper in combination with a sprayer and roller); U.S. Pat. No. 4,215,949 (discloses a vehicle with an asphalt supply hopper, burner, tack oil sprayer and a tamper); U.S. Pat. No. 3,564,985 (discloses a unitary vehicle carrying asphalt and propane heaters for the purposes of pavement repair); U.S. Pat. No. 4,198,177 (illustrates a unitary vehicle for repair of asphalt surfaces including an emulsion tank containing a water soluble, air cured sealer bonding agent and an air compressor driven by the vehicle engine. The vehicle cooling liquid is used for heating the emulsion to a useable temperature while the compressor sprays the emulsion on the surface to be repaired.)
U.S. Pat. No. 4,362,586 discloses a polyamide resin which is used as a primer for highway repairs using asphaltic membranes. The polyamide primer acts as a moisture barrier and promotes bonding to the cementitious substrate. The patent further discloses that the primer extends the low temperature range for adhesive tack. In using the method, a cracking asphalt is filled with a crack filling material. The road substrate surfaces on opposite sides of the crack are then cleaned of loose debris followed by the application of the polyamide primer which is applied in a solvent solution such as anhydrous isopropanol. An asphaltic membrane with an adhesive layer is positioned so that the adhesive layer is in contact with the prime surfaces and spans the filled crack. German Pat. No. 2,134,811 discloses a heatable roadway surface made of an underlayer of bitumen asphalt or concrete which is made by a combination of several steps. The base to be coated is first purified followed by vacuum treatment of the base to remove liquid from the capillaries. An epoxide resin and a hardener under pressure is impregnated into the surface. Heat is applied followed by the imbedding of a heating system in an epoxide mortar which comprises an epoxide resin, hardener, and a filler. Also relating to the field of road construction materials is U.S. Pat. No. 4,240,946 which relates to a preparation of a bituminous binder on the basis of bitumen and polyolefin. The mixture is prepared by a hot mix. This patent also discloses a road construction material using the binder with the inorganic additive material being heated (before being mixed with the binder) to a temperature below the decomposition temperature of the binder. U.S. Pat. No. 3,336,252 relates to a process for the production of molding materials from bitumen and monoolefin polymers. U.S. Pat. No. 3,310,619 discloses the use of methlymethacrylate chips in PVC or PVC copolymer. The chips are encapsulated or permanently bonded without exhibiting excessive thermoplastic flow within a translucent vinyl matrix. U.S. Pat. No. 4,455,186 discloses a self-contained exothermic applicator and process wherein the reactants react exothermically when electrically ignited. The heat liberated by the reaction plasticizes a thermoplastic resin or cures a thermosetting resin to bond together two closely spaced objects.